Compression coding means a set of signal processing techniques for sending digitalized information through a communication line or storing digitalized information in a form suitable for a storage medium. Media, such as videos, images, and voice may be the subject of compression coding. In particular, a technique for performing compression coding on videos is called video compression.
Many media compression techniques are based on two types of approaches called predictive coding and transform coding. In particular, a hybrid coding technique adopts a method of combining the advantages of both predictive coding and transform coding for video coding, but each of the coding techniques has the following disadvantages.
In the case of predictive coding, any statistical dependency may not be used in obtaining predictive error samples. That is, predictive coding is based on a method of predicting signal components using parts of the same signal that have already been coded and coding the numerical difference between predicted and actual value. More specifically, predictive coding follows from information theory that predicted signals can be compressed more efficiently and may obtain a better compression effect by increasing the consistency and accuracy of prediction. Predictive coding is advantageous in processing non-smooth or non-stationary signals because it is based on causal statistics relationships, but is disadvantageous in that it is inefficient in processing signals at large scales. Furthermore, predictive coding is disadvantageous in that it may not use limitations of the human visual and auditory systems because quantization is applied to the original video signal.
Meanwhile, orthogonal transform, such as discrete cosine transform or discrete wavelet transform, may be used in transform coding. Transform coding is a technique for decomposing a signal into a set of components in order to identify the most important data. Most of the transform coefficient are 0 after quantization.
However, transform coding is disadvantageous in that it must depend on the first available data in obtaining the predictive value of samples. This makes it difficult for a prediction signal to have high quality.